<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="js/jquery-3.3.1.js"></script>
    <style>
        h2
        {
            position:fixed;
            left:100px;
            top:150px;
        }

        #dimScreen
        {
            position:fixed;
            padding:0;
            margin:0;

            top:-100px;
            left:0;

            width: 100%;
            height: 10%;
            background: rgba(88, 234, 252, 0.5);
            transition: all .5s ease-in;
        }
    </style>
    <script>

        function show() {

            $("#dimScreen").animate({top:'0'},100);

        }
    </script>
</head>

<body>

<h2>测试</h2>
<button onclick="show()">ceshi2</button>
<br/>
<div id="dimScreen">
    <button >ceshi</button>
</div>


</body>
</html>